As to an ink-jet recording method, high-resolution images are possible to be recorded by a relatively simple apparatus, and the ink-jet image forming method has been rapidly in progress in various fields. Further, there are a wide range of applications to be utilized, and a recording medium or ink suitable for each purpose is employed.
Specifically, in recent years, recording speed has been largely increased, and printers each having convenience printing-strength properties have been developed.
In the case of this ink-jet recording system, ink is ejected from an ink-jet head, and deposited onto a recording medium to form images. The ink should exhibit low viscosity in order to eject the ink from the ink-jet head. On the other hand, high viscosity ink is demanded in order to prevent color mixing called bleed generated since plural kinds of ink each exhibiting different color are deposited on the recording medium.
As a method to solve this dilemma, a UV radiation curable ink-jet technique employing actinic energy radiation curable ink is practically utilized. This is a technique by which an actinic energy radiation curable monomer and a photo-polymerization initiator are added into ink, and the resulting one is exposed to actinic energy radiation after depositing it onto a recording medium to cure the ink, resulting in achievement of a good balance between acquisition of an ejection property and prevention of bleed.
On the other hand, as a technique to suppress bleed, there is an image forming method employing so-called hot-melt ink wherein the hot-melt ink is generally present as a solid phase, but is present at a high operation temperature of an ink-jet printing apparatus as a liquid phase, disclosed in Japanese Patent Document O.P.I. (Open to Public Inspection) Publication No. 2007-154188 and Japanese Patent Document O.P.I. Publication No. 2007-154189. In the case of this hot-melt ink system, when depositing ink-droplets on the surface of a recording material, they are rapidly solidified with no expansion of the recording material in the direction of the area, whereby high resolution images can be formed. Since actinic energy radiation curable ink as well as hot-melt ink does not contain a solvent in an ink component, images can be formed on a recording material exhibiting no ink absorption.
Further, disclosed is a technique by which a gelation action-producing material is contained in an actinic energy radiation curable ink component via temperature change in order to improve dot gain and glossiness, and images are formed via the temperature change and exposure to actinic energy radiation after ink ejected from an ink head is deposited on a recording material (refer to Patent Document 1).
Further, examples of an image forming method employing this ink include a technique by which heat-pressure is applied after printing, followed by exposure to UV rays (refer to Patent Document 2), and another technique of specifying time that elapses before exposure to UV rays after injecting ink in order to specify dot size and dot height after depositing the ink (Patent Document 3).
Among these, as to the technique described in Patent Document 2, for example, when heat pressure was applied after forming images, followed by exposure to UV rays, dot height to form images was suppressed, whereby the effect of resolving uncomfortable feeling of gloss was able to be confirmed, but there appeared a problem such that when cleaning was to be periodically done since members such as rollers used for fixing were contaminated via repetitive fixing thereof, so that the roller surface was scratched during operation, concavity and convexity thereof were transferred to the image surface, resulting in deterioration of image quality. Also, as to the case of a printing system in which an intermediate transfer medium is used, this phenomenon similarly produces a facing problem.
Further, as described in a document such as “Thermal Effect on the penetration of an ink droplet onto a porous medium (Masosheng Ren, Herman Wijshoff, 5th European thermal-Science Conference, The Netherlands, 2008)” the technique described in Patent Document 3 was insufficient to dissolve unevenness of image gloss by suppressing elevation of the image, since a much shorter period of time than 100 ms was only to be consumed until a liquid droplet temperature fell at a temperature around room temperature after high-temperature hot melt ink was ejected from an ink-jet head, and deposited onto a recording medium.
Accordingly, in the case of the above-described conventional technique in which UV curable ink containing a gelling agent is used, there often appeared the following problems: problems such that the resulting image exhibited insufficient intensity; evenness of image gloss was insufficient; and image density evenness specifically in a solid image among images was insufficient.